On January 1, 2020, If you fly below 18,000 ft in an aircraft with an electrical system, outside of class E airspace you will be required to; Broadcast your position data among other things (ADS-B Out) on 978mhz. If you fly above 18,000 feet; Broadcast your position data among other things (ADS-B Out) on a 1090mhz extended squitter transponder. (this unit is also acceptable below 18,000 ft)
WAAS is not a requirement, HOWEVER it is the only solution offered to the GA community with the accuracy to comply with 14CFR § 91.227.